[PATCH v1 1/2] PM: sleep: Avoid using pr_cont() in the tasks freezing code

Rafael J. Wysocki
2022-12-01T18:35:02Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Using pr_cont() in the tasks freezing code related to system-wide
suspend and hibernation is problematic, because the continuation
messages printed there are susceptible to interspersing with other
unrelated messages which results in output that is hard to
understand.

Address this issue by modifying try_to_freeze_tasks() to print
messages that don't require continuations and adjusting its
callers accordingly.

Reported-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
kernel/power/process.c | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)

Index: linux-pm/kernel/power/process.c
===================================================================
--- linux-pm.orig/kernel/power/process.c
+++ linux-pm/kernel/power/process.c
@@ -27,6 +27,8 @@ unsigned int __read_mostly freeze_timeou

static int try_to_freeze_tasks(bool user_only)
{
+ const char *what = user_only ? "user space processes" :
+ "remaining freezable tasks";
struct task_struct *g, *p;
unsigned long end_time;
unsigned int todo;
@@ -36,6 +38,8 @@ static int try_to_freeze_tasks(bool user
bool wakeup = false;
int sleep_usecs = USEC_PER_MSEC;

+ pr_info("Freezing %s\n", what);
+
start = ktime_get_boottime();

end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
@@ -82,7 +86,6 @@ static int try_to_freeze_tasks(bool user
elapsed_msecs = ktime_to_ms(elapsed);

if (todo) {
- pr_cont("\n");
pr_err("Freezing of tasks %s after %d.%03d seconds "
"(%d tasks refusing to freeze, wq_busy=%d):\n",
wakeup ? "aborted" : "failed",
@@ -101,8 +104,8 @@ static int try_to_freeze_tasks(bool user
read_unlock(&tasklist_lock);
}
} else {
- pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
- elapsed_msecs % 1000);
+ pr_info("Freezing %s completed (elapsed %d.%03d seconds)\n",
+ what, elapsed_msecs / 1000, elapsed_msecs % 1000);
}

return todo ? -EBUSY : 0;
@@ -130,14 +133,11 @@ int freeze_processes(void)
static_branch_inc(&freezer_active);

pm_wakeup_clear(0);
- pr_info("Freezing user space processes ... ");
pm_freezing = true;
error = try_to_freeze_tasks(true);
- if (!error) {
+ if (!error)
__usermodehelper_set_disable_depth(UMH_DISABLED);
- pr_cont("done.");
- }
- pr_cont("\n");
+
BUG_ON(in_atomic());

/*
@@ -166,14 +166,9 @@ int freeze_kernel_threads(void)
{
int error;

- pr_info("Freezing remaining freezable tasks ... ");
-
pm_nosig_freezing = true;
error = try_to_freeze_tasks(false);
- if (!error)
- pr_cont("done.");

- pr_cont("\n");
BUG_ON(in_atomic());

if (error)